An Upper Atmospheric Model for Solar Minimum Conditions

Abstract

An atmospheric model for the height range 100?700 km, likely to hold for solar minimum conditions, has been developed. The flux density of solar radiation at 10.7 cm wavelength (F10.7) is taken to be 70 ? 10?22 w m?2 (cps)?1. The model is based on extrapolation to 70 units, of density and density scale heights at different solar activity periods, in the height range of 250?700 km, deduced from drag observations of 46 satellites (King-Hele and Walker, 1961; Martin et al., 1961; King-Hele and Rees, 1963; King-Hele and Quinn, 1965) during the period 1958 (F10.7 ? 230 units) to early 1964 (F10.7 ? 80 units), for diurnal minimum and maximum conditions. In the range of 100?250 km, density values obtained from various rocket flights to early 1964 (F10.7?80 units) have been used. The model gives the distribution of neutral particles, i.e., n(O2), n(N2), n(O), n(He), n(H); atmospheric scale height (H); mean molecular mass (m?); atmospheric temperature (T) and atmospheric pressure (p) with height up to 700 km. Diffusive equilibrium for N2, O2 and O has been assumed to hold above 130 km, for He above 100 km and for H above 500 km. In the region of dissociation, observed values of n(O)/n(O2) of Schaefer and Brown (1964) have been adopted. The results are discussed and compared with those given by other workers.